Field of the Disclosure
The invention relates to blood separation systems and methods. More particularly, the invention relates to systems and methods for depleting platelets from blood during a blood treatment procedure.
Description of Related Art
Various blood processing systems make it possible to separate blood into two or more constituent parts, which may be useful for donation purposes and for treatment of individuals with potentially detrimental or harmful blood conditions or disorders.
When such systems are used for blood component donation, whole blood is typically drawn from a donor, the particular blood component or constituent is removed and collected, and the remaining blood constituents are returned to the donor. By thus removing only particular constituents, potentially less time is needed for the donor's body to return to normal, and donations can be made at more frequent intervals than when whole blood is collected. This increases the overall supply of blood constituents, such as plasma and platelets, made available for health care.
Similar procedures may be performed to treat individuals with potentially detrimental or harmful blood conditions or disorders. For example, thrombocytosis is a blood condition in which too many platelets are produced by the body and may be caused by either a bone marrow disorder (which may be referred to as “essential thrombocytosis”) or, more commonly, by some other underlying cause (e.g., a major surgery, such as a splenectomy), in which case the condition may be referred to as “reactive thrombocytosis.” Depending on the severity of the condition, thrombocytosis may lead to potentially life-threatening thrombotic events, such as heart attacks and embolisms. Thus, in cases of extreme thrombocytosis, the health of a patient may be improved by removing a portion of the platelets of their blood.
Whole blood is typically separated into its constituents through centrifugation. This requires that the whole blood be passed through a centrifuge after it is withdrawn from, and before it is returned to, the source. To avoid contamination of the blood and possible infection of the source (if the source is a living donor or patient), the blood is preferably contained within a sealed, sterile fluid flow system during the entire centrifugation process. Typical blood processing systems thus include a permanent, reusable centrifuge assembly containing the hardware (drive system, pumps, valve actuators, programmable controller, and the like) that spins and pumps the blood, and a disposable, sealed and sterile fluid processing assembly that is mounted in cooperation on the hardware. The centrifuge assembly engages and spins a disposable separation chamber of the fluid processing assembly during a collection or treatment procedure. The blood, however, makes actual contact only with the fluid processing assembly, which assembly is used only once and then discarded.
As the whole blood is spun by the centrifuge, the heavier (greater specific gravity) components, such as red blood cells, move radially outwardly away from the center of rotation toward the outer or “high-G” wall of the separation chamber of the fluid processing assembly. The lighter (lower specific gravity) components, such as plasma, migrate toward the inner or “low-G” wall of the separation chamber. Various ones of these components can be selectively removed from the whole blood by forming appropriately located channeling seals or barriers and outlet ports in the separation chamber of the fluid processing assembly.
According to one conventional approach to therapeutic platelet depletion, blood in a single-stage separation chamber is separated into red blood cells, plasma, and a “buffy coat,” which contains blood constituents having an intermediate specific gravity, including platelets and white blood cells. The buffy coat is continuously removed from the separation chamber and conveyed to a waste container, while the separated plasma and red blood cells are returned to the blood source. While such a procedure has proven to be effective in treating extreme thrombocytosis, there are some potential drawbacks, as the buffy coat includes not only the targeted platelets, but also white blood cells and smaller red blood cells. Additionally, due to this being a continuous process, the waste volume generated may be larger than desired (e.g., on the order of approximately 1000 mL per procedure), which requires costly replacement fluid to be conveyed to the blood source to maintain fluid balance.
Accordingly, it would be advantageous to provide systems and methods that are capable of depleting platelets from blood without the potential drawbacks associated with the conventional approach.